Process of and apparatus for wetting bulk materials



Sept. 9, 1969 w, LODIGE EI'AL 3,466,015

PROCESS OF AND APPARATUS FOR WETTING BULK MATERIALS Filed Jan. 4, 1968 3 Sheets-Sheet 1 Fig. 7

Sept. 9, 1969 w, LQDIGE ETAL PROCESS OF AND APPARATUS FOR WETTING BULK MATERIALS Filed Jan. 4, 1968 3 Sheets-Sheet 2 Sept. 9, 1969 w, LQDIGE ETAL 3,466,015

PROCESS OF AND APPARATUS FOR WETTING BULK MATERIALS Filed Jan. 4, 1968 5 Sheets-Sheet 5 United States Patent 3,466,015 PROCESS OF AND APPARATUS FOR WETIING BULK MATERIALS Wilhelm Lodige, Fritz Lodige, and Josef Lucke, Paderborn, Germany Filed Jan. 4, 1968, Ser. No. 695,676 Claims priority, application Germany, Jan. 11, 1967,

1m. (:1. B01f 15/00, 7/04 US. Cl. 2599 13 Claims ABSTRACT OF THE DISCLOSURE A process of and apparatus for wetting bulk materials capable of trickling movement by treating them in a multichamber apparatus having a rotatable knife head in each chamber at least one of them being in a hollow shaft through which the wetting liquid is introduced.

The invention relates to the wetting of bulk materials. The invention is particularly, but not exclusively, applicable to the glue-coating of dry materials capable of trickling movement such as pulverulent and/ or very fine-fibre or fine-grain materials. Liquid, such as glue, is continuously added to a flow of material to which a turbulent movement is imparted for mixing purposes.

In various branches of industry it is necessary for liquids to be uniformly added to highly absorbent, and generally powdered, dry materials; one example is the chipboard industry. Recently, in the production of chipboards, grinding dust or very fine chips have been used as a covering layer for the boards. A binding agent such as glue with between 12 and 20% by weight of solid resin constituents is added to this covering layer material. The glue liquid used usually consists of about 50% (by weight) of water and about 50% (by weight) of solid resin since in this way a relatively fine division can be achieved, such as is desirable.

Known apparatus for covering grinding dust or very fine chips with glue are chip gluing mixers in which the chip material is circulated in a mixing container by rotating mixing tools without substantial friction on one another. The glue is sprayed through a plurality of twocomponent nozzles as an air-glue mixture on to the material to be wetted in the upper portion of the mixing container which can be for example elevated or provided with outward bulges. However, the glue distribution is not satisfactory, since owing to non-uniform distribution of liquid and binding agent and accretions falling off the mixing tools, more or less large agglomerates form in the mixing material and these agglomerates harden very quickly. In order to eliminate such mixing defects as much as possible, rotating teasing rollers or similar tools have been arranged in the gluing mixers, but owing to the large quantity of material in the mixing container only a proportion of the agglomerates can be taken-up and opened before they harden.

The mix must, therefore, after glue application, be homogenized in separate machines if it is desired to avoid having glue spots in the finished products. Such subsequent homogenization, however, is generally not satisfactory since, by this time, the mixed material has already solidified the glue by absorbing its water content to such an extent that the glue can no longer be openedout.

The known homogenizing machines and gluing mixers are also expensive and the mixers, and particularly their two-component nozzles, are very liable to develop faults in operation when dealing with fine to powdered material.

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An object of the present invention is to provide a process and apparatus with which it is possible for even very fine dry materials to be uniformly wetted without subsequent treatment whilst avoiding agglomeration, for example with a glue liquor with a degree of fineness and a uniformity such as has not been satisfactorily possible hitherto.

Other objects of the present invention and advantages thereof will become apparent as the description proceeds.

Accordingly, the invention provides a process for the wetting of bulk materials capable of trickling movement, wherein a liquid is continuously added to the flow of material subjected to turbulent movement for mixing purposes, the dry material being introduced continuously in succession into a plurality of mixing stations in each of which a stirring action takes place and the liquid being added to the material in the mixing station before the last station or at least one of them. The mixing stations have the efiect of loosening-up the material, uniformly providing it with wetting liquid and then mixing it uniformly. The mixing achieved is substantially better than is achieved with the hitherto known gluing m xers, the knife-type mixing tools having the additional advantage that they open-up old agglomerations in the mix and, despite the addition of liquid, prevent the formation of new agglomerations until the mix is in the desired state.

According to another aspect of the invention, there is provided an apparatus for carrying out the mixing and homogenizing process comprising a plurality of small mixing and homogenizing chambers connected to one another through apertures and arranged in succession to one another, and a mixing and homogenizing tool is rotatable in each chamber to stir the material therein, the tool in at least one chamber being mounted on a hollow shaft provided with apertures through which liquid can flow.

The shaft of the first and/or second knife head is provided with a plurality of knives or knife-like mixing tools distributed along its length and is conveniently a hollow shaft with radial bores. The bores can be extended externally by small tubes. When liquid glue is introduced into the hollow shaft as it rotates at a high speed, for instance by means of an electromotor, the glue is distributed as a film on the inner wall of the hollow shaft. As a result, small quantities of liquid are continuously projected through the radial bores into the mixing and homogenizing chamber in which it is introduced into the material being mixed which is being whirled aboutr the chamber. The material preferably rotates as a ring of material adjacent the chamber wall. If the radial bores of the hollow shaft are extended outwardly by small tubes, the liquid distribution is substantially improved owing to the increased peripheral speeds of the outlet apertures, so that the liquid impinges substantially in the form of a mist on the inner side of the loose ring of material being mixed, and penetrates therein. Since the ring of material is continuously sliced-up by a plurality of obliquely set knives rotating at a high speed, for instance by means of an electro-motor connected with the shaft carrying the knives, and is turned over at the same time, the particles of material are continually rubbing against one another and pass on any excess glue which they have received to neighbouring particles which have received less glue, before the glue has lost its ability to spread owing to the water content being absorbed into the dry material being mixed.

After the addition of the glue, the mixture must also pass through further chambers with knife heads in order to continue the mixing operation as long as possible. Only when the material being mixed has almost completely absorbed the water content of the glue and the mixture is almost dry again and therefore capable of trickling movement, can the material issue from the apparatus. In order not to have the material passing too quickly through the chambers, which are connected to one another by apertures, it is expedient to make some or all of these successive knife heads rotate in the opposite sense and, if appropriate, also to make the individual knife heads rotate at different peripheral speeds or rotational speeds.

In one embodiment of the invention, five mixing and homogenizing chambers are arranged one behind the other. Each cylindrical chamber has a diameter of 250 mm. and a length of 250 mm. The knife head in the first chamber after the feed worm rotates at a peripheral speed of about 16 metres per second by means of a suitable drive means such as an electro-motor. The dry material introduced in this chamber is distributed over the appropriate working width. Agglomerations present in the material are opened-up. In the adjoining second chamber the liquid is added to the material being mixed. Here, by way of a suitable drive means, the knife head rotates at a peripheral speed of about 32 metres per second for better distribution of the liquid. In the third and fourth chambers the knife heads rotate at a peripheral speed of about 16 metres per second, again by way of a suitable drive means. The knife head in the last chamber has a relatively low peripheral speed of only about 8.5 metres per second, i.e. the drive means connected with the shaft carrying said knives is driven at a lower speed. The discharge of the mixed material from this last mixing and homogenizing chamber is restricted by a weight-loaded swingable gate so that this chamber operates with a greater degree of fullness than the preceding chambers. In this way, the degree of fullness necessary in the preceding chambers is maintained and the time of dwell of the material in the entire apparatus is prolonged so that the wetted material can absorb the liquid more deeply in order to prevent agglomerations forming during and after the mixing operation.

It is also advantageous to arrange the mixing tools in each chamber in such a manner that they sweep over the entire peripheral surface and are so set that, alternately from chamber to chamber, 60 to 90% of the material is conveyed in the axial sense e.g. towards the left and to 40% towards the right, so that the material passes through the apparatus along a zigzag course as seen in plan view.

This apparatus serves, for example, to apply glue to very fine chips with an output of 500 to 700 kilograms per hour. With the addition of 30% by weight liquid glue (solid resin'content 50% by weight) the material issues from the apparatus mixed in a satisfactory uniform manner and in an agglomeration-free condition capable of trickling. For higher outputs per hour, the mixing and homogenizing chambers must be appropriately enlarged. If necessary, the chambers can be capable of being cooled in order to dissipate friction and reaction heat and/or heatable in order to accelerate reaction.

One embodiment of the invention is illustrated diagrammatically in the accompanying drawings, wherein:

FIGURE 1 is a longitudinal sectional view through mixing and homogenizing chambers and a feed worm conveyor of an apparatus for wetting and homogenizing fine bulk materials and FIGURE 2 is a cross-section through a mixing and homogenizing chamber taken on the line 22 of FIG- URE 1.

FIGURE 3 is a top-view with partly opened mixing chamber of the apparatus of FIGURE 1.

FIGURE 4 is a lateral view of the apparatus of FIG- URE 1 with partly opened mixing chamber and conveyor screw casing.

The apparatus illustrated comprises a housing 1 with a lower wall 2 and an upper wall 3, connected to one another by side walls 4. The housing 1 is closed by end walls 5 and 6.

The end wall 6 has a central aperture in the end wall 6 through which a tube 7 extends into the housing. A worm conveyor 8 is rotatable in the tube 7 by means of a motor not shown, connected to the conveyo shaft. The conveyor screw 8 introduces bulk material into the apparatus in the direction indicated by the arrow 9. The speed of the worm 8 is infinitely variable by means of a suitable gear not shown and presses the material into a first, approximately cylindrical, mixing and homogenizing chamber 10. This chamber 10 has a concentric shaft 11 of a knife head or other mixing tool which is provided with sharp-edged knives 12 or mixing tool arms distributed over its length. The shaft 11 is connected with an electromotor 11a. The knife head 12 or other tool distributes the introduced material uniformly over the length of the chamber 10 or the width of the housing 1.

The material to be mixed is forced from the chamber 10 into a further cylindrical mixing and homogenizing chamber 14 through a radial aperture 13. The axis of the chamber 14 is parallel to that of the chamber 10. A hollow shaft 15 which carries knife-like mixing tools 12 is mounted concentrically in this chamber 14 and is connected with the electro-motor 150. The shaft 15 also carries small tubes 16 which project radially outwards and which are each arranged behind one of the tools 12 which, advantageously, have relatively short arms 12a in the direction of rotation of the shaft. These small tubes 16 are used for introducing liquid into the material situated in the chamber 14. The chamber 14 is followed by further chambers 17, 18, and 19 which are each connected to one another by means of an aperture 13. A shaft 11 is arranged in each of these chambers connected with electromotors 11a. Each shaft 11 has arms for mixing tools 12, the arrows shown in the drawing indicating that these mixing tools in some cases rotate in opposite senses.

The last chamber 19 is provided with a discharge aperture 20 which can be closed or throttled by a gate 21. A displaceable, but fixable, weight 23 is mounted on a bar 22 on the outer side of the gate 21, so that the resistance of the gate 21 to the pressure of material exerted on it from the inside of the chamber 19 can be adjusted. The quantity of material forced out of the chamber 19 is adjustable by varying the magnitude of this resistance. The material is discharged over a plate 24 through a discharge shaft (not shown) or on to a conveyor (also not shown). The gate 21 can pivot outwards about a hinge 25.

Owing to the adjustable gate 21, the material accumulates in the last chamber 19 so that in all the preceding chambers the desired degree of fullness in each case can be maintained despite continuous operation. A further acumulation of material in the mixing chambers is caused by the fact that the knife head rotating in the last chamber 19 rotates in the same direction as the knife head in the previous chamber 18, whereby the material circulated in the last chamber 19 opposes the passage of material through the preceding chambers. In the same sense, the material can also be made to accumulate in one of the preceding chambers or in several chambers in succession.

A hollow space is formed between the chambers 10, 14, 17, 18 and 19 and the walls 2, 3, 4, 5 and 6 of the housing 1. This hollow space can be used to receive a heating or cooling medium. For this purpose, inlet pipes 27 and outlet pipes 28 are provided in the housing 1.

FIGURE 2 shows on a larger scale the mounting of the knife head with the hollow shaft for the introduction of the wetting liquid. The hollow shaft 15 is connected with the electro-motor 15c and is mounted at one end in an overhung fashion on a stub shaft 29 and has mixing tool arms distributed at its outer periphery and is several rows over the length of the hollow shaft 15. These arms are advantageously somewhat shortened knife-type arms 12a. Tools 12b follow these arms in the direction of rotation and extend almost to the peripheral surface of the chamber and have a widened head 120. Small tubes 16 for spraying-out the wetting liquid are also arranged on the hollow shaft 15. These small tubes 16 are arranged above bores 30 in the hollow shaft 15 and extend radially outwards. Each small tube 16 is arranged behind a knifetype arm 12a and before a following tool arm 12b. The upper end of each small tube 16 can be provided with a notch-like cut-out 16a which extends in the direction of rotation of the shaft 15. The tool arms 12a arranged in front of the small tubes 16 are longer so that the liquid does not reach the chamber wall.

A fixed feed conduit 31 projects into the hollow shaft 15, through its Open end 15a, and serves for introducing the wetting liquid. This conduit 31 is fixed and is supported on a bearing bracket 32 which is arranged at the outer side of one side wall 4. The underside of the feed conduit 31 is provided with outlet apertures 33 which are followed by small outlet tubes 34. The wetting liquid from these tubes 34 passes to the inner wall of the hollow shaft 15 and, owing to the rotation of the hollow shaft 15, is finely divided at the inner wall until it passes through the apertures 30 and the following small tubes 16 into the interior of the cylindrical mixing chamber. In order to prevent the hollow shaft 15 drawing in any dust or foreign bodies with the air, the open end 15a is closed by an air filter 15b.

What we claim is:

1. In a process for the wetting of bulk materials capable of trickling movement, the steps comprising transferring bulk material through a succession of a plurality of mixing stations in each of which the bulk material in transit is subjected to turbulent stirring; continuously adding a liquid internally of said bulk material while undergoing turbulent movement, said liquid being added to said bulk material in at least one mixing station prior to the final station, and thereafter mixing the bulk material-liquid combination under turbulent movement without further liquid addition.

2. A process according to claim 1, wherein the mixing and homogenizing operation is repeated in successive stations until the liquid is absorbed by the dry material and the mixture is free of agglomerations and capable of trickling movement.

3. An apparatus for carrying out mixing and homogenizing comprising in combination a plurality of peripherally enclosed individual bulk material stirring chambers arranged in side-by-side relation and connected to one another by material transmitting apertures, material entry means in the first of said chambers, material exit means in the last of said chambers, stirring tool means in each chamber rotatable on an axis disposed transversely to the overall direction of material flow through successive chambers, the tool means in at least one of said chambers being mounted on a hollow shaft, the axis of rotation of which is disposed transversely to the overall direction of material flow, said hollow shaft being provided with apertures through which liquid can flow.

4. An apparatus as claimed in claim 3, wherein an infinitely variable controlled-feed worm is arranged upstream of the first chamber for the purpose of introducing dry material.

5. An apparatus according to claim 4, wherein the hollow shaft, or each of them is open at one end and a fixed liquid inlet conduit projects into the shaft.

6. An apparatus according to claim 5, wherein the liquid throughfiow apertures of the hollow shaft, or of each of them are arranged on the hollow shaft to follow knives in the direction of rotation.

7. An apparatus according to claim 6, wherein the liquid throughfiow apertures are extended outside the hollow shaft or shafts by small tubes.

8. An apparatus according to claim 7, wherein the small liquid tubes are notched, the notches being arranged in the direction of rotation of the shaft.

9. An apparatus according to claim 3, the hollow shaft or shafts being arranged at right angles to the material flow in each mixing chamber.

10. An apparatus according to claim 3, wherein the last mixing and homogenizing chamber has an outlet aperture which can be throttled.

11. An apparatus according to claim 3, wherein the tools are knives some of which are relatively short and other knives are obliquely positioned and are arranged in such a manner that they sweep over the entire inner peripheral surface of the chamber and, from chamber to chamber alternately, convey to of the material being mixed in the axial sense towards one chamber end and 10 to 40% towards the other chamber end.

12. An apparatus according to claim 3, wherein the tools are knife heads which are driven in opposite directions of rotation.

13. An apparatus according to claim 12, wherein the tools are knife heads which rotate at different peripheral speeds.

References Cited UNITED STATES PATENTS 52,268 1/1866 Chapman 25925 98,226 12/1869 Bruce 25921 1,717,760 6/1929 Charnley 25926 2,239,753 4/1941 Martin 2596 XR 2,668,693 2/1954 Gard 2599 2,947,524 8/1960 Bridges 2596 3,343,814 9/1967 Mund 2596 WALTER A. SCHEEL, Primary Examiner JOHN M. BELL, Assistant Examiner US. Cl. X.R. 25925, 45 

